*{
    margin: 0;
    padding: 0;
}
html,body{
    /* 自适应高度 */
    width: 100%;
    height: 100%;
}
#main{
    width: 100%;
    height: 100%;
    /*背景色线性变化*/
    background: -webkit-gradient(linear, 0% 0%, 0% 100%,from(#ADD8E6), to(#f6f6f8));
    overflow: hidden;
}
span{
    /*强制不换行*/
    white-space: nowrap;
    position:absolute;
}
#mainScreen{
    width: 800px;
    height: 600px;
    margin: 8px auto;
    border: 1px solid gray;
    background-color: white;
    /*隐藏span标签超出oScreen屏幕范围的内容*/
    overflow: hidden;
    position: relative;
}
#bottom{
    width: 800px;
    height: 32px;
    margin: 5px auto;
}
#txt{
    width: 240px;
    height: 30px;
    line-height: 30px;
    font-family: 微软雅黑;
    padding-left: 8px;
    border: 1px solid lightslategrey;
    float: left;
}
#btn{
    width: 60px;
    height: 30px;
    line-height: 30px;
    margin-left: 30px;
    margin-top: 2px;
    border-radius: 4px;
    float: left;
}